Various types of test adapters are known which either connect to leads of a particular type of surface mounted package mounted on a printed circuit board or connect directly to terminals on a printed circuit board, where the terminals on the board are configured for accepting a particular type of surface mounted package. The adapter is, in turn, connected to a tester for testing the printed circuit board or the package itself. The adapter, thus, must contain electrical contacts which correspond to the terminal configuration of a particular type of surface mounted package intended for use with the printed circuit board being tested. Various types of adapters for connection between a printed circuit board and a tester are described in U.S. Pat. Nos. 4,862,076 and 4,564,251 and in U.S. patent application Ser. No. 08/079,721, entitled "Test Adapter for Packaged Integrated Circuits", assigned to the present assignee and incorporated herein by reference.
A very area-efficient type of surface mounted package which is increasing in popularity is a ball grid array package illustrated in FIG. 1. In FIG. 1, a packaged integrated circuit 10 contains a silicon die having its pads electrically connected to respective ones of conductive solder balls 12 distributed on the bottom surface of the package 10 in an array. A printed circuit board 14 has formed on its surface a corresponding array of conductive pads 16 which align with the array of conductive solder balls 12. Conductive traces (not shown) on printed circuit board 14 lead from each of the pads 16 to other circuitry on the board 14. To mount the package 10 to the board 14, the package 10 is positioned on top of board 14 and the resulting structure is heated until the solder balls 12 melt and fuse to the connect pads 16.
The ball grid array type packages provide a high density of terminals at a very low cost. Also, by not having any pins extending from the package, there is no risk of bending any leads and destroying the product.
The inventor is not aware of any adapters which emulate ball grid array type packages. The design of a ball grid array type adapter presents numerous problems. One problem is that the contact pads 16 and conductive balls 12 may be separated by a millimeter or less, which makes it extremely difficult to reliably provide individual connectors on an adapter for connecting to each of contact pads 16 without taking up any more area than the area of the intended package 10. Further, since the adapter must be soldered onto the contact pads 16 of the board 14, the heating process must not adversely affect the adapter. Thirdly, the adapter must be made inexpensively, since the user may choose to discard the board 14 after testing instead of spending time removing the adapter from the board 14.
What is needed is an inexpensive and reliable adapter which can connect to an array of contact pads on a board for emulating a ball grid array type package.